Collectively tauopathies including Alzheimer?s disease (AD) impact close to 6 million Americans and cost over $200 billion in medical care. They devastate families and cause victims to lose their memory, their dignity and, finally, their identity. Currently no disease modify agents exist for treating tauopathies, and AD and spontaneous recovery is unknown; a diagnosis of tauopathy is a death sentence. Strategies proposed to reduce tau burden include increasing clearance, decreasing phosphorylation or nitration, reducing aggregation, and diminishing inflammation, among others. Arginine metabolism is poised at a critical branch-point and serves as a precursor for nitric oxide generation from nitric oxide synthases or polyamine production from arginase (Arg1). Our data indicates that Arg1 overexpression in a mouse model of tauopathy reduces multiple aspects of the tau phenotype; phospho-tau deposition, Gallyas staining, hippocampal atrophy, high molecular weight tau multimers, tau nitration, cytokine markers of inflammation, inhibitors of autophagy, and protein kinase activation. Many of these effects can also be demonstrated in cell culture. We also show that higher- order polyamines directly block tau aggregation and promote microtubule assembly in solution at physiological concentrations, but acetylated polyamines fail to mimic this affect. Several distinct effects of this manipulation could mediate these remarkable benefits of Arg1 over expression and polyamine metabolism. The goal of this application is to better understand how polyamines contribute to the benefits of reducing the tau phenotype, and identify other potential targets for treating tauopathies and possibly AD. Utilizing gene therapy, mouse models of tauopathy, and knockout models we will test four aims. 1) Determine if Increased Polyamines Diminish Tau Pathology. 2) Determine if Reduced Polyamines Enhance Tau Pathology. 3) Test if Pharmacological Nutritional Modulation of Polyamines Regulates Tau Pathology and 4) Test if the Deletion of SSAT Reduces Tau Pathology. Success in these aims will increase our knowledge regarding the role of polyamines metabolism in regulating the tau phenotype. Our goal is to identify additional therapeutic targets that could be regulated by pharmacological agents to arrest or slow the progression of the tau deposition in humans with neurodegenerative disease.